Haleigh Ann Carrigan, 21, is being held at the Placer County Jail after officers went to her South Sacramento home, where they say they found some of the stolen items.

The managers of Sierra Regency Retirement Living said Tuesday they spent many hours studying surveillance video and invested more than $20,000 in cameras and other equipment to figure out who was stealing from their residents.

"If you're doing this to seniors, they are so vulnerable -- and it was just disgusting to me," said Mary Dustin, the executive director of Sierra Regency.

Dustin said she purchased 32 cameras for the facility, added them to the 16 cameras already on site, and began watching surveillance video last summer. At first, she said, she only noticed a suspicious car, but later, cameras captured someone wearing a mask.

Yet, the person wasn't entering through the front door, but rather, through a side entrance and with a key, she said.

Finally, more video led to a shot of an unmasked person driving the same suspicious car and staff realizedit was the granddaughter of one of the residents, Dustin said.

Dustin and Roseville police said the suspect would visit during the day, then return at night to steal.

"(She was) going into apartments that had been left unlocked for a short period of time and stealing the keys,and then she'd come back in the middle of the night and burglarize the residents while they were sleeping," Dustin said.